Hemodynamic variables were evaluated in 4-month-old normotensive Wistar Kyoto rats (WKY) and spontaneously hypertensive stroke-prone rats (SHRSP) that had been maintained for 3 months on one of four experimental diets, standard (STD: 24% crude protein), low protein (LP; 19% crude protein), high protein (HP; 32% crude protein), or high methionine (Met; 1.9% methionine). WKY/STD and SHRSP/LP had similar body weights (BW) that were significantly higher than those of SHRSP/STD, SHRSP/HP and SHRSP/Met. The heart weights (HW) of SHRSP/LP were significantly higher than those of the other experimental groups. The HW/BW ratio for WKY/STD was significantly less than that for any of the SHRSP groups, while the HW/BW ratio for SHRSP/LP was significantly higher than that for SHRSP/HP and SHRSP/Met. The systolic blood pressure (BPs) of all SHRSP groups was significantly higher than that of WKY/STD, while the BPs of SHRSP/STD was significantly higher than that of SHRSP/Met, SHRSP/HE and SHRSP/LP. The diastolic blood pressures (BPd) of WKY/STD, SHRSP/Met and SHRSP/HP were the same but significantly lower than those of SHRSP/STD and SHRSP/LP. WKY/STD and SHRSP/Met groups had similar mean arterial pressures (MAP) that were significantly lower than those of SHRSP/HP, SHRSP/STD and SHRSP/LP. The relative total peripheral resistance (TPR) in WKY/STD, SHRSP/Met and SHRSP/HP was similar but significantly lower than that of SHRSP/STD and SHRSP/LP. The results of these experiments indicate that the increased MAP in SHRSP fed either a standard rat diet or a low protein diet was due to increased TPR, while a high protein diet led to nearly normal MAP due to a reduction in TPR.